The number of suicides in the nation's two largest state prison systems is ticking upward, and authorities in California and Texas are linking the increase to the rising number of inmates kept in solitary confinement.

In California, which has the largest state prison system with about 170,000 inmates, there have been 41 suicides this year, the most in at least six years and a 17% increase from 2005. Although an estimated 5% of California's inmates are housed in solitary confinement — also known as "administrative segregation" — 69% of last year's suicides occurred in units where inmates are isolated for 23 hours a day, according to state Department of Corrections records. About half the suicides this year were in such units.

In Texas' prison system, which has 169,000 inmates, there have been 24 suicides this year, up from 22 in 2005. Most of the inmates who killed themselves were in some form of solitary confinement, says John Moriarty, inspector general for the prison system.

Texas prisons also are reporting a 17% increase in attempted suicides: 652 so far this year, compared with 559 in 2005. The number of attempted suicides this year is the most in nearly a decade, according to state prison records. Statistics on attempted suicides in California prisons were not immediately available.

The figures from California and Texas are fueling a debate over whether solitary confinement is the best way to control or punish violent or dangerous inmates, particularly those who are mentally ill.

More than 70,000 of the 1.5 million inmates in state and federal prisons are kept in isolation, a reflection of get-tough policies designed to separate rival gang members and those who have gotten into fights while behind bars.

Isolated inmates typically have significant restrictions on visitors and get little help in dealing with the psychological problems that can be caused by isolation. They usually are allowed out of their cells for no more than an hour a day to exercise alone; their exposure to TV and reading material also is limited.

"Are we housing the mentally ill in prison facilities?" Moriarty asks. "I think the answer is yes. But I don't know if that's the best place for them to be."

Moriarty, whose office investigates every inmate death in Texas, says stress from isolation and increasing numbers of inmates with long sentences have contributed to the rise in suicides. "Length of sentence is a big factor. There is despair about not getting out."

The increase in inmate suicides in California has triggered recent changes in segregation units. In October, guards began checking inmates housed in solitary confinement every 30 minutes, rather than every hour, says Shama Chaiken, the state prison system's chief psychologist for mental health policy.

Some segregation cells also will be modified to remove shelving, vent openings and other features that offenders could use in hangings, the most common form of suicide in California prisons, Chaiken says. This month, California Gov. Arnold Schwarzenegger announced a $1 billion plan that includes 10,000 new beds in prison medical and mental health units.

A few jurisdictions have credited expanded mental health programs with reducing prisoner suicides. After Kentucky set up a mental health program for those in the state's 83 county jails in 2004, suicides in the jails fell 47%, according to The (Louisville) Courier-Journal.

There have been 13 suicides this year in the 188,000-inmate federal prison system, the same total as in 2005. Florida, the third-largest state system with 90,000 inmates, has had nine prison suicides this year; it had eight last year.